If you want updated or replacement system software for your Android or other device, you should check with your carrier, your device's manufactuer, and/or forums that are specific to Android.

If you want Firefox for Android, you can get it in the marketplace: https://play.google.com/store/apps/details?id=org.mozilla.firefox
If you want Android for development purposes, you can get it from the Android developer site: http://developer.android.com/index.html
If you want updated or replacement system software for your Android or other device, you should check with your carrier, your device's manufactuer, and/or forums that are specific to Android.